Research On Reliability Of Solder Joint Of Power Device IGBT Packaging

Insulated gate bipolar transistor,IGBT,as a common power device,has been widely used in the industrial field due to its advantages such as fast breaking speed and DC-AC conversion of electrical energy.The connection joint between the IGBT chip and the direct bonded-copper ceramic board plays a supporting and heat dissipating role in the packaging structure and is a weak part in the packaging structure.The connection joint is usually formed by a solder process.Therefore,the quality of the solder joint is an important factor affecting the reliability of the IGBT device.when the IGBT chip operates,heat generated due to power loss,as a common soldering process defect,voids reduce the heat dissipation performance,result in an increase in IGBT failure rate.At the same time,the IGBT device withstands temperature changes during operation,which may cause crack between the materials due to different thermal expansion coefficients,affect long-term reliability.Based on these problems,this article simulates the effect of void on heat dissipation,studies the effects of different process methods on void rate,and studies the changes during thermal shock,provide a theoretical basis for the reliability of IGBT devices.Firstly,the steady-state thermal simulation method was used to study the effect of voids on the temperature of the chip.Studies have shown that increasing the void rate will lead to an increase in maximum temperature;and the difference in the void location will have a certain effect on the maximum temperature;When the total void rate remains the same,As the number of voids increases,the maximum temperature will continue to decrease;At the same time,The temperature influenced by the distribution pattern when multiple voids exist.the increase of the thickness of the solder joint containing voids leads to the rise of the maximum temperature of chip.Secondly,the effects of two different soldering methods,both the hot plate reflow soldering and vacuum formic acid reducing atmosphere reflow soldering on the void rate were studied.Studies have shown that in the hot plate reflow soldering,the increase of the reflow temperature and the reflow time will lead to an increase in the void rate;The rougher the surface of the copper board,the smaller the void rate.in vacuum formic acid reducing atmosphere reflow soldering,the increase of peak temperature will lead to the reduction of void rate;when the solder joint thickness increase and the solder joint areas decrease,the void rate is reduced.Compare to hot plate soldering reflow,Vacuum formic acid reducing atmosphere reflow soldering can reduce the void rate largely.In the two soldering methods,92.5Pb5Sn2.5Ag solder has a lower void rate than Sn3.0Ag0.5Cu solder;the increase in the oxidation of the base material leads to an increase in the void rate,However,the increase of the void rate in the heating plate method is small,but in a reducing atmosphere reflow soldering will lead to a significant increase in the void rate.Finally,the thermal shock process in the temperature range of 0?175?is studied,The study found that at the initial stage of thermal shock,only Cu₆Sn₅ IMC was formed at the interface,As the number of cycles increased,Cu₃Sn+Cu₆Sn₅ IMC appeared,and the shape of the IMC gradually changed from scallop-like to flat-like,and the thickness of IMC gradually increased.When the number of cycles reaches 600,the direct bonded copper ceramic board cracks from the position of the upper copper layer,and it completely fails by 1000 times.